Some notes on the quasi-Newton methods

summary:A survey note whose aim is to establish the heuristics and natural relations in a class of Quasi-Newton methods in optimization problems. It is shown that a particular algorithm of the class is specified by characcterizing some parameters (scalars and matrices) in a general solution of a matrix equation

Two distinct transitions in a population of coupled oscillators with turnover: desynchronization and stochastic oscillation quenching

Synchronization, which is caused by mutual coupling, and turnover, which is the replacement of old components with new ones, are observed in various open systems consisting of many components. Although these phenomena can co-occur, the interplay of coupling and turnover has been overlooked. Here, we analyze coupled phase oscillators with turnover and reveal that two distinct transitions occur, depending on both coupling and turnover: desynchronization and what we name stochastic oscillation quenching. Importantly, the latter requires both the turnover and coupling to be sufficiently intense.Comment: 7 pages, 3 figures; typos corrected, references modified, acknowledgment added, author contribution added, abstract updated, and equations and figures displayed in a more readable manne

Development of a magnetically suspended, tetrahedron-shaped antenna pointing system

A magnetically suspended, tetrahedron-shaped antenna pointing system is proposed for use in a multibeam broadcasting satellite system in the future. The structure of this system is presented, along with its design concept and the functional test results which were obtained in a laser tracking system in the laboratory. According to these results, it has been confirmed that the system has many advantages over conventional systems and excellent performance

Severe Facet Joint Arthrosis Caused C7/T1 Myelopathy: A Case Report

Cervical myelopathy is caused by degenerative processes of the spine including intervertebral disc herniation and posterior spur usually developing at C3/4 to C5/6. C7/T1 single level myelopathy is very rare because of the anatomical characteristics. Facet joint arthrosis can be a cause of cervical myelopathy but only a few cases have been reported. The authors report an extremely rare case of C7/T1 myelopathy caused by facet joint arthrosis. A 58-year-old male presented with hand and gait clumsiness. The radiological examinations revealed severe C7/T1 facet joint arthrosis with bony spur extending into the spinal canal, which compressed the spinal cord laterally. The T1 spinous process indicated nonunion of a “clay-shoveler's” fracture, which suggested that his cervico-thoracic spine had been frequently moved, and thus severe arthrosis had occurred in the facet joints. A right hemilaminectomy of C7 and C7/T1 facetectomy with single level spinal fusion led to complete neurological improvement

Midterm results of extensive primary repair of the thoracic aorta by means of total arch replacement with open stent graft placement for an acute type A aortic dissection

ObjectivesWe sought to describe the midterm results of extensive primary repair of the thoracic aorta by means of the modified elephant trunk technique with a stent graft for acute type A aortic dissection, particularly the changes of the false lumen shown by enhanced computed tomographic scanning.MethodsThe subjects were 35 consecutive patients who received arch replacement with open stent grafting for type A acute aortic dissection between December 1997 and April 2002. The mean follow-up period was 55 months (range, 30-83 months). Computed tomographic scanning was performed at 1, 3, 12, and 36 months postoperatively to detect thrombosis and obliteration of the false lumen after its exclusion by the stent graft. The diameter of the aorta was measured at 3 levels: the distal edge of the stent graft, the diaphragm, and the origin of the superior mesenteric artery.ResultsTwo patients died in the initial operation, but no patients required additional surgical treatment of the thoracic aorta. The mean diameter of the stent grafts was 26.2 mm, and the mean length was 8.9 cm. Thrombus formation in the false lumen was recognized at the distal edge of the graft in all patients, at the diaphragmatic level in 26 patients, and at the superior mesenteric artery level in 15 patients. Obliteration of the false lumen was recognized at the distal edge of the graft in all patients, at the diaphragmatic level in 20 patients, and at the superior mesenteric artery level in 15 patients. The aorta distal to the stent graft showed minimal changes.ConclusionsIn patients with acute type A aortic dissections, it is possible to perform extensive primary repair of the thoracic aorta with relative safety by using a synthetic graft with a self-expanding stent, and this method might reduce the necessity of further operations not only for the distal descending aorta but also for the thoracoabdominal aorta